One of the best Netflix original series I've seen. There are quite a few negative reviews and I honestly felt the same way to begin with, I'd originally only made it to episode 2 before I gave up on the series but I convinced myself to give it another try and I am so glad I did. By around episode 3/4 it really does massively improve and the series has left me wanting to purchase the books and hoping for a second series.
If you're a fan of BBC's Merlin, Witcher or Game of Thrones then you will not be disappointed by this series, it takes the best elements of all 3 and combines them with a really interesting alternative version of the Arthurian Legends.